Clamping operation is crucial in the semiconductor packaging industry for securing a pre-form in between moulds before resin compound is delivered thereto to encapsulate a semiconductor device. Good control over the clamping operation is important to ensure that the pre-forms are not scratched or damaged during the clamping operation and that sufficient clamping force is applied to minimize leakage of the resins during the moulding operations of the packaging process.
Variety of mechanical devices have been used and proposed to improve the control of the application of force. Because the required clamping force is high, i.e., about 60 tons, and the tolerance is relatively small, i.e., a few tons, the clamping mechanism must be capable of exerting extremely high force and with high degree of accuracy. Currently, a popular choice is to use a hydraulic-type of a press. Hydraulics is a good choice for this type of operation as the force output is substantially linear to the input. This allows the operator to more easily and accurately apply the right amount force needed for the operation. Furthermore, hydraulic systems are able to exert high amounts of force.
However, hydraulic systems suffer from a number of shortcomings, particularly in light of the clean-room environment in which semiconductor packaging processes are often operated under. Hydraulics systems by its physical nature, requires the use a fluid. A common fluid currently used is a kind of oil. When exerting high amounts of force, and particularly in a continuous and repeated manner, the fluid and its fumes have the tendency to leak out the system. This leakage, while may not be a significant in an industry such as automobile repair, can be a serious problem in the semiconductor packaging industry where cleanliness is a high priority. In addition, hydraulic systems often involve complex parts and mechanisms which need precision in mating, and which need relatively high maintenance.
Although there exist other means for exerting high amounts of force, e.g., pneumatic or electromechanical presses with toggle mechanism, these systems are not ideally suited for clamping operations in semiconductor packaging. Some exemplary shortcomings include, among others, inability to exert high amounts of force; lack of control, accuracy, or precision; non-linear relationship between input and output; complex parts or mechanisms; high need for maintenance; excessive friction between parts; inefficiency; slow operations; etc. Therefore, in light of the shortcomings stated above, there is a need for a new type of force-exerting device which can controllably deliver high amounts of force without compromising the cleanliness of the environment which it is operated under, and which avoids complex mechanisms or high maintenance.